I recently switched over to Debian on my desktop computer (thx @Hypfer for convincing me to do this). One of the first issues I ran into was the fact that after I mounted my encrypted external harddrive it was only readable for the root user. The cause of this is that I start Veracrypt via gksudo because otherwise I was not able to mount my drives since my main user is not in the sudoers list.
The solution to that is to create an exception for the user that you want to mount the volume with:%[group of your user] ALL=(root) NOPASSWD:/path/to/veracrypt
After that all users in this group are able to mount volumes with Veracrypt and access the content.